In a highly-charged personal statement to the House of Commons following his resignation as Foreign Secretary, Mr Johnson did not make a direct challenge to Mrs May’s position as Prime Minister and Conservative leader.

But he denounced the plan agreed at Chequers and set out in the PM’s white paper last week as a ‘Brexit in name only’ which would leave the UK in a state of ‘vassalage’.

Accusing the Government of ‘dithering’ over its Brexit negotiations, he said that a ‘fog of self-doubt’ had descended on Mrs May’s stance to EU withdrawal since she first set it out in a speech at Lancaster House last year.